The discussion revolves around the concept of tension in a rope, particularly in the context of a car pulling on the rope while moving at a constant velocity. Participants are exploring the relationship between force, acceleration, and tension, questioning their intuitions and assumptions regarding these physical concepts.
The discussion is active, with participants sharing various perspectives and examples to clarify their understanding of tension. Some have offered insights into the nature of forces acting on the rope, while others express confusion about the initial problem statement and the assumptions being made.
There are uncertainties regarding the initial conditions of the problem, such as whether the rope is taut or slack at the start and how the car begins to move without acceleration. These aspects are under scrutiny and contribute to the complexity of the discussion.
well , we don’t give answers, but here’s A hint: in the equation f= ma, f is the net force acting on the rope. So if a is 0, net force is zero, and if the car is pulling with a force on the rope, there must be another force acting on the rope to give a net force of 0. What is it? Surely you’ve seen a vehicle trying to pull another out of the mud, and neither vehicle is moving in spite of the first one with pedal to the floor, and the rope is pretty tight , right?Pi-is-3 said:
This description is most unclear.sumitsumit said:
Does the car suddenly go from stationary to speed v? How does it "start to move" with no acceleration?Pi-is-3 said:
I have no idea how it starts. I didn't start the thread @sumitsumit did. Honestly I am more confused by what @PhanthomJay said.haruspex said:
The correct equation is Σf=ma, i.e. the acceleration results from the sum of all forces. The tension in the rope is only one force on the car; there may be others.Pi-is-3 said:
Well perhaps here is a better example...a game of ‘tug of war’. Your team is pulling on one end of the rope, trying to move the opposing team. And the opposing team is pulling the rope on the other end, trying to move your team. But assume strengths and foot holds of each team are the same, so no one is going anywhere. It’s a stalemate. There is no acceleration. Now you are trying to tell me there is no tension in the rope? There is a lot of tension , the rope might be close to breaking if it’s not strong enough. Think about Newton’s first law and draw a free body diagram of the rope from one end to an imaginary cut in-the center.Pi-is-3 said:
Now I get it. Thanks!PhanthomJay said:
Please tell me that you believe that you can’t have a force without acceleration.Pi-is-3 said:
